P. 1. Move Phil Masters and Chris Owen from the Playtesters credits to the Additional Material and Research Assistance credits. Also, add Robert Meehan and Troy Leaman to the Additional Material and Research Assistance credits.

P. 6. Replace the last three lines in the first paragraph with: "– either the molecules adenine and thymine (an AT pair) or cytosine and guanine (a CG pair)."

P. 55. In the first paragraph, the reference to Gengineered Advantages should point to pp. 31ff.